Patent GB-234940-A (GB)
Title: Improvements in and relating to apparatus for and method of measuring and recording vector quantities
IPC: G01R11/48
Filed: 1923-12-06
Abstract: 234,940. White, A. E., (Sangamo Electric Co.). Dec. 6, 1923. Roller-and-slot recording apparatus; feeding and driving means; special quantities, registering.-A method of measuring and recording vector quantities consists in advancing a record sheet in accordance with the measured values of one vector quantity and moving a stylus across the sheet in accordance with the measured values of another vector quantity so as to determine the angle points of a 'series of triangles whose sides are proportional to the two vector quantities and their resultant. The recording elements are moved by constantly-acting motors, the movements being controlled by the measuring instruments and the apparatus is shown applied to an alternating-current power meter which plots vectorially on the record sheet the apparent power and the reactive component of the power. Two polyphase watt-hour meters are used, one of which, E, measures the true power and controls the horizontal movement of the record sheet 26, whilst the other, R, measures the reactive component of the power and controls the vertical movement of a rack-bar 50 carrying the stylus 49. The stylus thus traces out a vector representing apparent power, and is returned quickly to zero at equal time intervals, marking during this movement a vector representing the reactive component of the power during the time interval. Independent constant speed motors 27, 52 drive the strip and stylus respectively through friction clutches 32, 61, the speed of the motors being such that they tend to drive the parts faster than if they were driven direct by the meters so that the burden of moving the parts never falls upon the meters. A rewinding drum 22 for the sheet 26 is driven b the motor 27 through the friction clutch 32, the sheet passing over a platen roller 23 and a controlling roller 24 driven by the meter E and having pins 25 piercing the sheet so that it is prevented from moving faster than the roller 24. The motor 52 drives through gearing a shaft 56 carrying two worms one of which, 58, drives through the friction clutch 61 a shaft 63 carrying a pinion 65, meshing normally with the verticallymovable rack bar 50, and a pinion 64 whereby the speed of the shaft 63 is controlled from the meter R through gearing 66, 68, 70. The other worm 57 on the shaft 56 rotates a hollow shaft 79, Fig. 10, through which extends an independently rotatable shaft 81 the bearing 82 of which is in the form of an eccentric fixed to the shaft 79. Looselv mounted on the eccentric 82 is a pawl 83 adapted to be intercepted by one of two fixed stops 84, 84<a>, and a spiral spring 85 has one end fixed to a pin 90 on the pawl and the other end fixed to the shaft 79. As the shaft 79 rotates the spring 85 is wound up and the pawl is retracted bv the eccentric 82 until it is free of the stop 84, when it will swing through 180‹ and be moved by the eccentric into a position to engage the stop 84a. This intermittent movement of the pawl 83 at equal time intervals is communicated by an arm 89 to a cam 86 adapted to rock a bell-crank lever 72 in which the end of the shaft 63 is mounted so that the pinion 65 is disengaged from the rack-bar 50, an arm 71 of the bell-crank lever taking in a notch 77 of a latch lever 75 to retain the pinion 65 clear of the rack. The rack bar is thus permitted to drop to its initial position, whereupon a pin 78 on the bar moves the latch lever 75 downwards to release the arm 71 from the notch 77 and allow a spring 74 to return the pinion 65 into engagement with the rack. Since the return movement takes place very quickly the line traced by the stylus 49 will be approximately perpendicular to the movement of the strip, giving a vectorial representation of the reactive power. A series of triangles is thus traced out from which the apparent power, true power, reactive power and power factor may be read.